Renting a car can sometimes bring up the same fears as buying one. You constantly worry about being had, about the next guy getting the best deal, questions about where to rent, the gas, the late fees or even early fees. Sometimes it seems there is no way to win if you're on a budget. So we set out to see if you could get taken for a ride. In our series ""nightline" for the lookout". Reporter: Okay, let's talk about rental cars. Somehow, a fairly simple task turns very complicated. Two bucks more. Can we just take the compact? Reporter: And expensive, with each of the add-ones, the gas, insurance, and gps, these charges can reach into the hundreds if you're not careful. So three lookout jeeps, that three days, traveling over 500 miles, renting cars in between, finding the best ways to save cash when burning rubber. Our adventure begins in the big easy. David estes runs a website that compares rental prices. I can't wait to rent a car. Reporter: We split into teams and hit the road to find the answers to some of the most burning rental car questions. Ready? Reporter: And with our hidden cameras strapped on? All right, guys, good luck. Reporter: Our first question, is it more cost-effective to rent at the airport or rent in town? I stay here and head straight for the avis counter. While I'm here, dave heads to the avis location downtown. We're heading to the avis downtown. Reporter: So just to make it interesting, we send the producers downtown also. We make them take more for two a person, so which of us got the best deal? In the end, the taxi fare downtown was worth it. The base rise for my rental was $40 higher for the rental, and in addition, I had to pay for airport fees. David, our cool consumer, is watching closely with an eagle eye. That is seven dollars. I think I will have to come back. That will be fine. Reporter: Our producers, meanwhile? I think it is better a half mile away. Reporter: Finally, they straggle in after spending an hour on the bus. They are forced to upgrade to a larger car because it was the only one left. I'll put you in this. Reporter: But they still paid less than me, in fact, $80 less for the same car. Fact number one, it is usually cheaper to rent outside the airport. With a couple of lessons learned, we head to the next stop. On the road again &#9834; Reporter: Jackson, mississippi, the city where our next question was, doesn't really matter if you book in advance. We want to test if it is cheaper to book in advance. One of our teams booked ahead of time, I just booked ten minutes ago. And you haven't booked at all. You're booking the exact same car to see if it will be cheaper. Okay, here we are. We want to know if you have a car available. I can get this for you. You're very kind. How are you doing? How are you? Booking under david estes, i booked just ten minutes ago. Reporter: Then the three teams gathered in the garage. All right, what did you get? I got 220? What did you get? 201. 279. Does this make sense, or is this totally arbitrary? Reporter: Take away number two, putting my unbelievable luck aside, david says you will save the most money by booking as far in advance as possible. Taking this one to the bank. Reporter: Another day, another rental car scenario. Your car again. Reporter: This time, our caravan of tiny cars left for memphis, tennessee. We made it, in memphis, tennessee. Reporter: We're there to ask our next question, what happens if you return a car very, very early or just a couple of hours late? I guarantee if you return your car, even just two or three hours late you will get charged a whole day. Do you think you will get charged if you bring it back early? If you book it within a week and return it in two days i don't know what will happen. I'm really interested to see what happens there. Reporter: So were we, all three teams head to the counter to rate identical cars, I will return my early, the producer shows up late, and david will be right on time. And just four hours later when i return my week-long rental I was slapped with a $20 fee for being early. When my producers dropped off their car two hours late, they were charged a ten dollar an hour late fee, plus taxes. That is 60 bucks. David returns his car right on time and keeps his wallet closed. Tip number three, dropping off early is usually better than dropping off late. But returning it when you say you willis the only sure-fire way to avoid the fees. All the driving and lessons learned, it is time to do a rental car math. We were charged different fees at the rental car company we visited. But you if we followed david's advice, we would have been charged only seven fees. If we used his tips every step of the way, pumping our own gas and paying the basic insurance fee, we would have saved $100 per rental. We have done three tests with the different rental companies, we survived the drive, the road trip, four different cities in two days, now we're going to let someone else drive for us. Taxi? Nice, matt, thanks to matt gutman and the tip for that report. If you're like me and wondering whether to get the insurance, it is always a good idea to check with your credit card company first. You can get all the tips for the cheapest rental car at our website at abcnews/carrental. And next, in the public eye.

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